RIDERS07a-C-06DEC00-EZ-MC. (l-r) Jude Siapno and Clarence "Chuck" Mabanag, two Oakland cops known as "The Riders" enter the Alameda County Superior Court in Oakland today. Photo by Mark Costantini/Chronicle ... more

A former Oakland police officer, testifying in his defense in the retrial of the Riders, acknowledged Monday that he had beaten a man on the soles of his feet but denied beating him under a desolate freeway overpass.

Police said they had arrested Delphine Allen on June 27, 2000, on suspicion of selling drugs near 32nd and Market streets. Allen then began banging his head against a metal cage that separates police in the front seat of the patrol car from suspects in the backseat, said ex-officer Jude Siapno, 36.

"I saw Delphine bang his head on the cage," Siapno testified in Alameda County Superior Court in Oakland, where he and two other fired officers are on trial for beating suspects, planting evidence on them and falsifying reports. "I believed at the time he was injuring himself. He was trying to split his head wide open."

Siapno testified that he had tried to stop Allen from hurting himself because the then-officer feared he would be blamed for Allen's injuries. He said that as he tried to help Allen, the man kicked him in the chest with both legs.

The former officer used his flashlight to beat Allen on his bare feet, Siapno said, a method of "pain compliance," to force him into a patrol car because a crowd was gathering, and police wanted to leave the area as a safety precaution.

Clarence "Chuck" Mabanag, 39, Matt Hornung, 33, and Siapno are being retried on corruption charges after a jury in 2003 acquitted the three of eight charges and deadlocked on the remaining 27 charges. A fourth fired officer, Frank Vazquez, 48, the alleged ringleader of the Riders, is a fugitive.

Under questioning Monday by his attorney, Bill Rapoport, Siapno said he had learned later that Vazquez had doused Allen with pepper spray.

Allen has testified that police planted drugs as evidence and beat him twice when he protested his treatment. Allen said he had been attacked so severely that he couldn't walk unaided that day.

Siapno, an ex-Marine, denied that he and Vazquez had taken Allen to a remote area on Wood Street under Interstate 880 and beaten him.

In his cross-examination, Deputy District Attorney Terry Wiley accused Siapno of misleading the jury by testifying that he had grown up and gone to schools in a low-income West Oakland neighborhood and that he had built a rapport with Matthew Watson, a youth he is also accused of beating -- and was later killed in a carjacking.

In fact, Wiley charged, Siapno had lived with his family near 14th and Jackson streets, just blocks from Lake Merritt and the courthouse.

Siapno replied that according to police districts, everything west of Lake Merritt is considered West Oakland.

The prosecutor asked Siapno -- who has said he became an officer after seeing police at work as a youth -- whether he ever saw officers jump out of vans and slap people, yell profanities at them or falsify reports "while growing up."